Telephone system



IN VE NTUR EDUARD WOCHINGER ATTORNEY E. wocHlNGER lIIELEPHONIE. SYSTEM Filed July s, 1935 Jan. 26, 1937.

Patented Jan. 26, 1937 UNlTED STATES ATENT OFFICE TELEPHONE SYSTEM Application July 8, 1935, Serial No. 30,380 In Germany July 13, 1934 5 Claims.

The present invention relates to a circuit arrangement for selectors in long distance communication systems especially telephone systems and aims at increasing the line testing efficiency lin selectors having automatic setting, this being achieved in that the testing circuit of the selector is closed after each switching step of the selector.

In the drawing a subsidiary exchange UA, without batteries is shown as an embodiment of the invention. This has access to a main exchange HA over the connecting line consisting of two' leads. The connection of the subsidiary exchange subscribers toI this connecting line takes place over a selector DBIO, which for outgoing calls acts as a call finder, and for incoming calls is set by numerical impulses as a nal selector. In the normal condition of the system relay LIB, (and further relays LII, LIZ in case the contacts to be provided for each subscriber cannot be operated by one relay), is operated over one lead `of the -connecting line. These relays connect all the subscribers of the subsidiary exchange in common to the calling circuit through their working contacts and on deenergizing which occurs when a subscriber calls, cause a switching over of the calling circuit so that the individual subscribers can be tested. In order to reduce the number of relays of this kind to a minimum, contacts operated mechanically by the selector of the subsidiary exchange are used for this purpose, for exchange lwIB (I-I 1) and which are opened on the rst switching motion of the selector DBIB and remain open until position I l.

The setting of selector DBIB in the subsidiary exchange UA always takes place under the control of the main exchange HA, both in the case of outgoing calls, when the selector is acting as a call finder, and also` in the case of incoming calls when the selector is acting as a iinal selector.

As already mentioned, in the normal condition of the system relay LIB, and also relays LII and LI2 are energized, over the circuit: earth, relays LIZ, LII, LIB, wiper a in position B, winding I of relay UIB, lead a of the connecting line, contacts 2'IcIB, SSanIB, wiper dIVIB in position B, contact 43MB, winding I of relay XIB, battery, earth. In this circuit only relays LIB, LI I, and LI2 are energized, while relay XIB does not receive sufficient current.

Outgoing tralc When subscriber AI of the subsidiary exchange takes up his receiver the following circuit is set up: earth, contact ZB'LLIB, winding II of relay UIB, wiper b in position B, lead bI, subscriber AI, lead al, contact lwIB (I-I'I), wiper a in position B, winding I of relay UIB, lead a, contacts 2'IcIB, 391mm, wiper (IVIB in position B, contact 43mm, winding I of relay XIB, battery, earth. Besides the transitory energizing of relay KIB relay XIB also energizes in this circuit and locks up by the closing of contact 42IB in series with its winding II. The circuit just described passing over the a lead is opened at contact 43MB. In the subsidiary exchange relays LIB, LI I and LIZ release so that the switching magnet Wit of the selector in the subsidiary station is connected to the b lead over contact 23LIB. The following circuit is thus set up through the main exchange, earth, contact 23LI B, switching magnet WIB, contact 22uIB, lead b, contacts ZlicIB, 8g/IB, relay KIB, battery, earth. In this circuit both the switching magnet in the subsidiary exchange and also relay KI B in the main exchange are energized so that the switching device in the subsidiary exchange is advanced one step. Contact 521cI B switches on the switching magnet DIH in the main exchange through contact 53MB, so that the wipers DIIB to dIVIB, operated by this switching magnet, also advance one step. Through contact 51dIB which is operated each time switching magnet DIB energizes, relay YIB is energized over: earth, contact B'IdIB, resistance Wz`4, winding I of relay YIB, battery, earth. Thereupon the energizing circuit of switching magnet WIB and relay KIB, cornpleted over the b-lead of the connecting line, is broken at contact 48yIB. Switching magnet DIB is likewise disconnected by the opening of contact 527cm. The interaction would if necessary be repeated again and accordingly both the switching device BDIB in the subsidiary exchange and also the switching device in the main exchange would be advanced in step.

Since, however, the subscriber AI of the subsidiary exchange, connected to the rst contact is calling, the testing relay PIB, which after the occurrence of each step is connected to the a-lead over contact 45yIB, is energized in the main exchange after the rst step. This testing circuit is completed through earth, contact ZBuIB, winding II of relay UIB, wiper b in position I of lead bl, subscriber AI, lead al, wiper a in position I, winding I of relay UIB, lead a. of the connecting line, contacts 2IcIB, 39a1LIB, Wiper DIUIB in position I-I I, contacts 44mm, 45yIB, relay PIB, battery, earth. In the same circuit relay Uit is energized in the subsidiary exchange. By the closing of contact piii relay Yi ii is next maintained energized over its 'winding I, while by the opening of contact 22am the switching magnet Uli) of the switching device in the subsidiary exchange is out off. The earth previously connected over contact Etui@ is replaced by earth connected over contacts 24cm, iig/iii, iiikl and choke coil drii, by the opening of contact Etui@ and the closing of contact Qiuiil, so that complete symmetry exists between th-e two speaking leads, and no imbalance occurs in the subsidiary exchange. By the closing of contact Slpi a loop is also closed for seizing the exchange connecting devices, so that for example a preselector can be set in operation after whose setting relay Cor is energized. The subscriber receives a dialling signal. I-le can then commence dialling.

On operating the dial the relay PI@ in the main exchange used for testing while the selector is being set releases intermittently according to the impulses, while relay Uli) in the subsidiary exchange remains energized on account of its construction as a slow acting relay. Relay Yi similarly holds up in the main exchange during the impulse emission. Contact 3mm transmits the impulses to the connecting devices of the main exchange by interrupting the line loop. On the first release of relay Pi relay Vle is influenced since contact Sixt@ is also closed. The latter relay insures a clean transmission of the impulses by short circuiting the choke coil Dri at contact Stole during the emission of the impulses, and disconnecting the condensers (contacts 2811i@ and 2911MB).

The connecting devices oi the main exchange are set in the desired direction by the various impulse trains in any suitable manner, with which we are not concerned, and the desired subscriber is then rung in the known way.

It should be noted that the meters of the subsidiary exchange subscribers are centralized in the main exchange. In order now to be able to influence the corresponding meter when a subscriber sets up a call the meter is connected over a wiper of the switching device in the main exchange which controls the setting of the selector in the subsidiary exchange and is thus advanced in step with the letter. When the conversation has finished a meter impulse is transmitted over the lead c, in any way, with which we are not concerned, which iniluences the meter SME allocated to the calling subscriber. A second winding of relay Yiii lies in the meter circuit and on energizing maintains the connection existing between the main exchange and the subsidiary exchange so that even when the calling subscriber replaces his receiver no release of the selector DBI in the subsidiary exchange or of the switching device in the main exchange can take place during the metering process. If :at the moment that the selector of the subsidiary exchange is engaging a subscribers line during the further switching and after the termination of the conversation of the subscriber of the line in question, takes up his receiver, the connecting line leading to the main exchange can immediately be seized again. Since the selector of the subsidiary exchange has advanced in step with the switching device in the main exchange, in this case also the meter corresponding to the subscriber reached is again connected to the c- Ii a new call does not take place, both switching devices are advanced to vposition H through the alternating play of the above mentioned relay. In the main exchange relay Hli energizes in this switching position over contact Styli), wiper III-ie and resistance WIT, and by opening contact 5311i@ prevents the switching magnet dil] from being operated again and the consequent further switching of the corresponding wiper. The switching magnet Wit in the subsidiary exchange is further operated, however, by the alternate play between relays KH) and YH), since the corresponding selector has to carry out 17 steps to reach the zero position. This is continued until the selector DBIU in the subsidiary exchange reaches position I?. In this position relays Lit, and LH and Li? now energize over: earth, relays LI2, Ll i, and LIU, wiper a` in position l i, winding I of relay UIQ, lead a of the connecting line, contacts 21cm, would, lilhl, re-

sistance Wi, battery, earth. Relay Ll cuts oitl the operating circuit of switching magnet WIB, at contact 23H9, so that relays KIQ and Ylll in the main exchange can also no longer energize. By the opening of contact BB1/Iii relay I-IIU deenergizes and opens the circuit for the L-relay passing over a-lead, at contact ahi. Thereupon this relay again deenergizes. Through the closing of Contact 231A@ the operating circuit of switching magnet V l0 passing over the b-lead of the connecting line is again closed so that the selector in the subsidiary station makes one switching step (into the normal position). By relay KH) energizing in the operating circuit of switching magnet W l0 the switching Vmagnet of the switching device in the main exchange is now operated over contact 521cm, so that this switching device also makes one step, likewise into the normal position. Thus both are now standing again in position 6. On reaching this positionthe condition existing when the system is at rest is again set up (L-relay energized).

The number of steps of the selector in the subsidiary exchange are known to be larger than the number of steps of the switching device in the main exchange. Since, however, in order to actually connect up the meter of the calling subscriber through the switching device in the` main exchange, the switching device and the selector in the subsidiary exchange must be synchronous, the arrangement is such, as described above, that the motion is synchronous until the 11th contact, i. e., until the rst Contact without any subscribers connection, whereupon the selector in the subsidiary exchange travels over the remaining contacts and then accomplishes the last switching step together with the switching device. This release motion is achieved in that up until the 11th contact the relays KH), YH] and the magnet DID produces impulses for advancing both switching devices, whereupon the magnet Dill is disconnected from the impulse producing circuit and by a switching over process (Hi il) impulses are only produced through relays Kia and YI@ for the magnet WHO. In position il this then causes a reversal of the changeover device so that for the last switching step the circuit rst operative comes into operation again, together with the switching magnet DH).

Incoming trafic The subscribers attached to the subsidiary station can obviously also be called from the main station. The last digit of their call numbers corresponds, for example, to the number of steps encarecwhich Vthev selector DBIU VinY the Vsubsidiary exchange' must lbe taken in order to be set on their connections. If they were previously subscribers Vhaving individual lines to the main exchange they 7carrretain their original call numbers unaltered.

Only the c-lead from the nal selector has to be disconnected from their previous connections and led to a contacter wiper cZIiil. The a and bleads of all subscribers lines incoming from the iinal'selector are connected together in parallel. Thus both subscribers attached to the same level of a iinal selector and also those attached to diierent levels of the same nal selector or in particular to different final selectors, are incorporated in the subsidiary exchange while maintainingV their call numbers.

If a final selector (not shown) is set in any manner on the line leading to the subsidiary exchange for Athe purpose of calling subscriber A5, testing is carried out, in the known way, over the lead c5 thus seized, as to whether the line leading to the apartment house exchange is free. If this is not the case wiper cIIIlilhas left its position so that the lead c5 incoming from the nal selector is open and the calling subscriber receives an engaged signal in the known way.

If on the contrary the line leading to the subsidiary exchange is free relay Anl!) is energized over the lead c5, (lead c5, resistance Wi9, contact cm, relay Anie, wiper dlIIi in position 0, resistance Wii, battery, earth.) Relay Anl!! lies in a circuit dependent upon wiper dIlIIG, via contact Blame. ing of contact 39anill the circuit existing for relays Liil, Ll! and LEZ in the normal condition of the system is broken, so that these relays deenergize. Seizing from the subsidiary exchange is not possible since relay PHJ which is otherwise used for testing is disconnected and the selector is brought to rest through setting the switching device in the main exchange under the control of the seized testing lead. By the closing of contact 23MB after the release of relay Ll the operating circuit for the switching magnet passing over the b-lead is closed in series with relay KIS. Both switching devices now move synchronously as was described above for the case of the call of a subscriber of the subsidiary exchange. The advancement now, however, takes place until the wiper @IIS comes to rest on the calling lead c5. When this occurs relay CIS energizes over the circuit: lead c5, wiper dIi, contact 320mm, relay Cl Ei, battery, earth. By the opening of contact Ziele the operating circuit of magnet Wi@ and also the control circuit for the magnet DIG are broken. The speaking leads are switched through to the final selector by the closing of contacts 25cm and 26cm. The ringing current is transmitted tothe desired subscriber from the iinal selector in any of the known ways, and passes over the a-lead of the connecting line to the subscribers station in the subsidiary exchange and the earth in the subsidiary station connected over contact 20ml). If the ringing current were connected over the lil-line, then obviously the a and b-leads must be interchanged.

When the called subscriber replies the ringing current is disconnected by the completion of the loop in the iinal selector, and by the energizing of relay UH) over the speaking leads. Contact Zlui is closed so that now the lead b of the, connecting line is also switched through Through the open-l tothemain exchange. The desired subscriber is now connected to the calling subscriber.

After the termination of the conversation lead c5 is cut off from the final selector in any desired way, so that relays CIB and Anil), which had established a locking circuit over contact 35cm, release. In the subsidiary exchange relay UIB is deenergized so that the operating circuit for magnet W!!! in the subsidiary exchange and for relay KI D in the main exchange is again completed over the B-lead of the connecting line. By relay Klo, the magnet Dl of the selector in the main exchange is switched on through contact 527cm. Thus the reciprocal play between the two switching devices, already described, causes the advancement into the normal position in the manner described in the case of the release for an outgoing connection.

Special circuits If the selector in the subsidiary exchange is displaced from position il by hand, the two switching devices thus become out of step, relays LH), Ll l, Ll2 deenergize since the normal circuit is broken at wiper a of the selector. The magnet WED is connected in an operating circuit through the closing of contact 23Li0, the circuit being completed 'as in the case of a call over relay KIS in the main exchange and the lead b of the connecting line running between the main exchange and the subsidiary exchange. The magnet Dii! in the main exchange is switched on by relay KI 0, so that both switching devices are advanced under the control of the impulse circuit in the main exchange. Since in this case both switching devices are not synchronous the possibility of a subscriber who hangs up during the advancement into the normal position, causing the connecting line leading to the main exchange to be seized, must be prevented, for otherwise the meter of another subscriber would be operated in the main exchange. This is prevented in that through the displacement of the selector in the subsidiary exchange by hand, in contrast to the procedure in a normal call, relay XIB is energized in the main exchange, so that the testing relay PIU in the main exchange is not connected over contact 44mm, i. e., this relay cannot test and thus the advancement of the switching device into the normal position cannot be interrupted. For the rest the release motion occurs in the same way as after the normal establishment of a call, i. e., advancement in step until the eleventh contact of the switch in the main exchange is reached, then the selector of the subsidiary exchange is Controlled alone until position I7 and then the last step to the zero position is accomplished by both switching devices in common. The two switches are thus again in corresponding positions.

The same switching operations take place when the switching device of the main exchange is displaced from the zero position by hand.

In this case the wiper dIVIO cuts oi the alead of the connecting line so that relay XID cannot be energized. Seizing during the release motion is thus prevented. By the interruption of the circuit existing in the normal condition relays Lli, LII and LIE again deenergize whereupon the magnet WI 0 in the subsidiary exchange is again connected to an operating circuit over contact 23LIO, and is influenced by the reciprocal play of relays KIS and Ylii, partly together with the switching magnet Dill in the main exchange, and partly independently, as mentioned above, until the zero position is reached. They can then operate synchronously again when the next call is set up.

Each seizing of the devices in the main exchange can be indicated by a seizure lamp L. If desired, each seizing direction can be indicated specifically, of the contacts ml@ for the outgoing seizing and 561ml il for the incoming seizing are wired separately.

Having described the invention, what is considered to be new and is desired to be protected by Letters Patent will be set forth in the following claims.

What is claimed is:

1. In an automatic telephone system, a selector switch, a plurality of subscribers lines connected to said selector, means for automatically operating said selector step-by-step to hunt for a calling one of said lines, a testing circuit in said selector, means for closing and opening said testing circuit aft-er each step of said selector to test for the calling line, and means controlled by the testing circuit for stopping the automatic operation of the selector when the calling line is found.

2. In an automatic telephone system, a selector switch, a plurality of subscribers lines connected to said selector switch, a relay for producing impulses toautomatically operate the driving magnet of said selector to operate the switch in a step-by-step manner in Search of a calling one of said lines, a testing circuit in said selector, means controlled by said relay for closing and opening said testing circuit each time after said driving magnet has received an impulse, and means for stopping the operation of said switch when the calling line has been found.

3. In an automatic telephone system, a selector switch, a plurality of subscribers lines accessible to said switch, a relay for producing impulses to automatically operate the driving magnet of said selector switch to operate the same in a step-by-step manner in search of a calling one of said lines, a testing circuit in said selector switch, means controlled by said relay for closing and opening said testing circuit each time after said driving magnet has received an impulse and said switch has taken a step, means responsive to the closing of said testing circuit for opening the impulsing circuit of the driving magnet, and means for stopping said switch when the calling line is found.

4. In an automatic telephone system, a selector switch, a plurality of subscribers lines connected to said switch, a relay for automatically producing impulses tol operate the driving magnet of said switch step-by-step in search of a calling one of said lines, a testing circuit closed and opened by said relay each time said driving magnet has received an impulse and operated the switch one step, said relay holding said impulse circuit open during the closure of said testing circuit, and means for stopping said switch when the testing circuit indicates that the switch has stopped on the calling line. Y

5. In an automatic telephone system, a selector switch, a plurality of subscribers' lines connected to said switch, means for automatically operating the driving magnet of said switch in search of a calling one of said lines, a testing circuit including a testing relay, a second relay for closing and opening the testing circuit at each step of said switch, a locking circuit for said second relay closed by said testing relay, and means responsive to the stepping of the switch on the calling line for stopping the operation of said switch.

EDUARD WOCHINGER. 

